1. Field of the Invention
The present invention relates to an image forming apparatus in which a lubricant is supplied to a cleaning target part from which a residual toner is removed by a cleaning member, and particularly to an image quality maintaining technique in such an image forming apparatus.
2. Description of the Related Art
A toner image formed on an image carrier in an image forming apparatus goes through a transfer process and ultimately shifts onto a recording medium (herein after referred to as a sheet). In this transfer process, all the toner may not perfectly shift. In such cases, a small amount of toner remains on the image carrier. In the case of an image forming apparatus employing an intermediate transfer system, the residual toner may adhere to a secondary transfer roller that has the function of pressing a sheet to an intermediate transfer member at a secondary transfer position.
In the image forming apparatus, the unwanted toner remaining on the image carrier and the member that contacts the image carrier (here referred to as a cleaning target part) must be collected. As means for collecting such residual toner, a technique of abutting the edge of a plate-like cleaning member (so-called cleaning blade) made of urethane rubber or the like to the moving direction of the moving surface of a cleaning target part by a counter (so-called “counter system”) is known. Also, a different abutment method from the counter system, that is, a trail system, is known. The toner collected by the cleaning member abutted in accordance with one of the counter system and the trail system is collected into a housing section.
Supplying a lubricant on the cleaning target part is known as a technique to stabilize the cleaning performance of the cleaning member in the techniques of removing the residual toner on the cleaning target part by using such a cleaning member.
The lubricant not only can serve to prevent the plate-like cleaning member from lifting but also can serve to improve the separability of the toner and thus enhance the toner removal effect by the cleaning member. Moreover, as the lubricant is used, the mechanical frictional force between the cleaning member and the cleaning target part is reduced and therefore advantages can be expected such as prevention of local edge cracking in the cleaning member, reduction in the quantity of friction, and prevention of toner fixation due to reduction in the quantity of heat generation.
Meanwhile, in the case of adjusting the image density or in the case where a large quantity of toner is transferred to a sheet, if a sheet jam occurs, the large quantity of toner is directly transferred from the intermediate transfer member to the secondary transfer roller. However, the toner removing capability of the cleaning member has its limitation, and the toner that the cleaning member has failed to remove, of the large quantity of transferred toner, is carried downstream from the cleaning member in the moving direction of the cleaning target surface.
In an image forming apparatus in which the lubricant supply unit that supplies the lubricant as described above is arranged downstream from the cleaning member in the moving direction of the cleaning target surface, if the residual toner enters the downstream side from the cleaning member in the moving direction of the cleaning target surface as described above, the lubricant supply performance of the lubricant supply unit may be adversely affected.
Moreover, depending on the quantity of the residual toner that reaches the lubricant supply unit, part of the residual toner pass through the lubricant supply unit and may appear as noise on the image formed by the image forming apparatus.